There are numerous websites that allow users/visitors to post content (such as comments to blog posts or news). The published post can be edited by the poster, but only for some amount of time (typically in the order of minutes). After that, the "Edit" button no longer appears and the post can't be edited.

My question is: what's the rationale for this behaviour? If it is technically possible to let the users editing their posts, why not offering this feature indefinitely?

5 Answers
5

We discussed this behavior once among our developers and came to the conclusion that the only valid reason for this could be, to conserve the consistency of the posts.

Consider the Stack Exchange sites for example. Sometimes I come across a comment saying:

What did you mean by x

However, when I read the question 10 times, I don't see x anymore. This means the break of referential integrity. In other words, sometimes you refer to something, which can be deleted or completely changed later. This is not good IMHO.

Not sure the question belongs here, but I might as well try answering it.

The reason for this is basically, that you don't want posts/comments to change once they have been responded to. For example on stackexchange, there is no such limitation on answers, therefore you do have quite a number of comments, that seem to make no sense, simply because the answer was edited ever since.
Now on SE this is not such a big deal, because for one, you can see the edit history to understand an obviously outdated comment, but more importantly, because SE is not a place for discussion. In a discussion, being able to change what you said can basically destroy the whole discussion. It invites moving the goalpost and many other manipulations, even after the discussion actually would have been concluded.

Simple answer: It's difficult to hold a conversation in a forum when comments are not sorted chronologically. When people are able to edit their comments after there have been replies, this often leads to people modifying their posts to reply to the responses posted later. This can quickly make the discussion thread impossible for new readers to follow. (Indeed, it's difficult even to determine what comments are new, when changes can happen anywhere in the thread!)

Limiting edits promotes serial comments, where each new post chronologically follows the previous, so that others can follow the thread of the discussion simply by reading from start to end.

The usual reason for allowing a short period where someone can perform edits is to let them fix typos or broken markup that they only notice immediately after posting.

Another big reason is spam -- one forum I was a moderator of had a rash of fake "fluff" posts that seemed pointless yet innocuous. Until something came along and edited the forum posts for more nefarious purposes. Pretty brilliant plan to be honest -- most forums pay lots of attention to stopping the bots from posting but editing was wide open with a little CURL action.